如何生成网页的略缩图？

1. 关键代码：

using System;
using System.Drawing;
using System.Windows.Forms;
using System.Threading;
using System.IO;
using System.Reflection;

namespace WebsiteThumbnail
{
    public class WebsiteThumbnailImageGenerator
    {
        public static Bitmap GetWebSiteThumbnail(string Url, int BrowserWidth, int BrowserHeight, int ThumbnailWidth, int ThumbnailHeight)
        {
            WebsiteThumbnailImage thumbnailGenerator = new WebsiteThumbnailImage(Url, BrowserWidth, BrowserHeight, ThumbnailWidth, ThumbnailHeight);
            return thumbnailGenerator.GenerateWebSiteThumbnailImage();
        }

        private class WebsiteThumbnailImage
        {
            public WebsiteThumbnailImage(string Url, int BrowserWidth, int BrowserHeight, int ThumbnailWidth, int ThumbnailHeight)
            {
                this.m_Url = Url;
                this.m_BrowserWidth = BrowserWidth;
                this.m_BrowserHeight = BrowserHeight;
                this.m_ThumbnailHeight = ThumbnailHeight;
                this.m_ThumbnailWidth = ThumbnailWidth;
            }
                                    
            private string m_Url = null;
            public string Url
            {
                get
                {
                    return m_Url;
                }
                set
                {
                    m_Url = value;
                }
            }

            private Bitmap m_Bitmap = null;
            public Bitmap ThumbnailImage
            {
                get
                {
                    return m_Bitmap;
                }
            }

            private int m_ThumbnailWidth;
            public int ThumbnailWidth
            {
                get
                {
                    return m_ThumbnailWidth;
                }
                set
                {
                    m_ThumbnailWidth = value;
                }
            }

            private int m_ThumbnailHeight;
            public int ThumbnailHeight
            {
                get
                {
                    return m_ThumbnailHeight;
                }
                set
                {
                    m_ThumbnailHeight = value;
                }
            }

            private int m_BrowserWidth;
            public int BrowserWidth
            {
                get
                {
                    return m_BrowserWidth;
                }
                set
                {
                    m_BrowserWidth = value;
                }
            }

            private int m_BrowserHeight;
            public int BrowserHeight
            {
                get
                {
                    return m_BrowserHeight;
                }
                set
                {
                    m_BrowserHeight = value;
                }
            }

            public Bitmap GenerateWebSiteThumbnailImage()
            {
                Thread m_thread = new Thread(new ThreadStart(_GenerateWebSiteThumbnailImage));
                m_thread.SetApartmentState(ApartmentState.STA);
                m_thread.Start();
                m_thread.Join();
                return m_Bitmap;
            }

            private void _GenerateWebSiteThumbnailImage()
            {
                WebBrowser m_WebBrowser = new WebBrowser();
                m_WebBrowser.ScrollBarsEnabled = false;
                m_WebBrowser.Navigate(m_Url);
                m_WebBrowser.DocumentCompleted += new WebBrowserDocumentCompletedEventHandler(WebBrowser_DocumentCompleted);
                while (m_WebBrowser.ReadyState != WebBrowserReadyState.Complete)
                    Application.DoEvents();
                m_WebBrowser.Dispose();
            }

            private void WebBrowser_DocumentCompleted(object sender, WebBrowserDocumentCompletedEventArgs e)
            {
                WebBrowser m_WebBrowser = (WebBrowser)sender;
                m_WebBrowser.ClientSize = new Size(this.m_BrowserWidth, this.m_BrowserHeight);
                m_WebBrowser.ScrollBarsEnabled = false;
                m_Bitmap = new Bitmap(m_WebBrowser.Bounds.Width, m_WebBrowser.Bounds.Height);
                m_WebBrowser.BringToFront();
                m_WebBrowser.DrawToBitmap(m_Bitmap, m_WebBrowser.Bounds);
                m_Bitmap = (Bitmap)m_Bitmap.GetThumbnailImage(m_ThumbnailWidth, m_ThumbnailHeight, null, IntPtr.Zero);                
            }
        }
    }
}

At any rate, the trick is to use the Windows Forms Webbrowser control. Contrary to what you may or may not have heard, this does not have to be situated on a container form - it can be used independently with 100% programmatic access. There are a couple of catches: First, being a Windows Form control, this must operate on an STA (Single Threaded Apartment) thread. This means you need to either set the "AspCompat = "true" attribute on the page that uses it, or you need to make the actual Webbrowser Navigate call to the target page on a secondary thread whose state has been set to STA. I chose the latter. The other gotcha is that the Webbrowser control does its navigation on more than one thread. The DocumentCompleted event handler is fired when the browser has fully loaded the target url, and therefore it is in this event that we want to do our business logic.

2. 示例程序下载

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